Surgical Infection Flashcards
What is an SSI?
A surgical site infection. It is one that develops at the operative site within 30 days of surgery or up to a year after surgery if implants are placed.
What are the signs of an SSI?
- Pain/ tenderness
- Localised swelling/ heat/ redness
- Discharge/ drainage from incision
- Systemic signs e.g pyrexia
- Wound dehiscence (breakdown)
- Abscess
What are the possible consequences of an SSI?
- Welfare problems
- Wound breakdown
- Prolonged recovery
- Delayed healing
- Systemic illness e.g. septicaemia
- Costs of prolonged treatment/ hospitalisation
What does the bacterial burden have to exceed in a wounds to develop an infection?
More than 10^6 bacteria per gram of tissue
What are the 3 sources of bacteria for a wound?
1) Exogenous
2) Endogenous
3) Nosocomial (infection picked up in hospital)
What is a HAI?
Hospital acquired infection or nosocomial
- infection acquired in hospital by a patient admitted for a different reason other than the infection.
What are the different stages for classification of surgical wounds contamination?
1) clean
2) clean-contaminated
3) contaminated
4) dirty
Describe a clean wound scenario
- Elective, non traumatic procedure done with no break in aseptic technique.
- No acute inflammation
- No entry to respiratory tract, GI or urinary tracts
- No requirement for perioperative or postoperative antibiotics
- UNLESS it lasted more than 90 minutes, orthapaedic implants were use or there was significant tissue trauma
- Skin contaminant bacteria often Staphylococcus spp.
Describe a clean- contaminated surgery scenario
- Minor break in aseptic technique
- Entry into respiratory tract, GI or urinary tracts without significant contamination
- Antibiotics administered, often a perioperative single dose IV
Describe a contaminated surgery scenario
- Traumatic wound more than 4 hours old
- Break in aseptic technqiue
- Spillage from viscus (GIT, pyometra, UG tract)
- Antibiotics needed, both peri and postoperatively
- Broad spec possibly including anaerobes
Describe a dirty (infected) surgery scenario
- Traumatic wound more than 4 hours old with devitalised tissue or foreign material
- Perforated viscus
- Bacterial infection, abscess, pus
- Antibiotics needed, therapeutic course not prophylactic
Describe the patient factors that influence the likelihood
- General health e.g. hypothyroidism?
- Hypoalbuminaemia
- Functional state of host defences (age, BCS, malnutrition, systemic disease,drug therapy e.g. corticosteroids)
List some surgical problems that can increase the chances of an SSI developing?
- Orthopeadic vs soft tissue surgeries have different risk levels
- Aseptic technique
- Duration of surgery
- Foreign material e.g. sutures/ implants
Why are sutures a site of infection?
- Foreign material= body reacts to it (inflammatory response)
- When implanted the sutures are rapidly coated with tissue protein which created sites for bacterial colonisation
- This colonisation can lead to biofilm formation
- Biofilm increases the difficulty of treating an infection
What is a biofilm?
A structured community of bacterial cells enclosed in a self produced polymeric matrix and adherent to an inert or living surface
-Once developed the biofilm let bacteria in to make it more resistant to antibiotics
What is quorum sensing?
When the bacteria in a biofilm communicate together
What are the 7 Halstead Principles?
1) Gentile tissue handling
2) strict aseptsis
3) Haaemostasis
4) Preservation of the blood supply
5) No tension on tissues
6) Good approximation of tissues
7) Obliteration of dead space
What perioperative factors increase chances of an SSI developing?
Aanesthesia- longer the GA the more risk
Drugs- Propofol is a lipid based emulsion and supports rapid bacterial growth in contaminated
Wound ischaemia- keep PCV above 20%
Shock/ trauma increase risk
Nursing- hygeine (handwashing), pain management, management of drains/ bandages/ cannulae
What are the most common bacterial skin flora in cats and dogs?
Dogs= Staphlococcal spp and streptococcal spp Cats= Pasteurella multocida
What are the most common bacterial flora found in the respiratory tract?
-Staphs and streps
What bacteria are likely found in the oral cavity?
Large number of aerobic and anaerobic species
What is the best use of prophylactic antibiotics for surgey?
- Work better if given at before surgery i.e. if its in the tissues before contamination occurs so administer before surgery - give IV during induction
- Usual protocol is to repeat dose every 90 mins intraoperatively and if contamination occurs or if drains/implants are used then extend to post operative treatments
Which antibiotics should you use for prophylatic treatment?
- Bacteriocidal NOT bacteriostatic
- Broad spectrum agent
- e.g. Clavulanate amoxicillin, Cefuroxime (2nd gen cephalosporin)
What is the procedure for monitoring the wound?
- Check surgical wounds after 24 hours and change dressing (wear gloves)
- Dressing should be changed every day or 48 hours
- Give owners clear advise and instructions
What should you do if you find an SSI?
- Obtain samples for C+S, broad spectrum antibiotics should be given until the results are available and then treatment plan adapted accordingly.
How do you treat orthopaedic infections?
- Initial signs involve soft tissues so you should aspirate and send for C+S
- Radiography for changes
- Remove implants if unnecessary, if they are needed for healing then treat with antibiotics for 6+ weeks until healed and then remove implants.
